Computational capability for physical reservoir computing using a spin-torque oscillator with two free layers
Computational capability for physical reservoir computing using a spin-torque oscillator with two free layers
复制标题
使用具有两个自由层的自旋扭矩振荡器进行物理储层计算的计算能力
DOI：
10.1103/physrevb.107.054406
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发表时间：
2023
影响因子：
3.7
通讯作者：
Taniguchi Tomohiro
中科院分区：
文献类型：
--
作者：
Yamaguchi Terufumi;Tsunegi Sumito;Nakajima Kohei;Taniguchi Tomohiro
报道了利用具有两个自由层的自旋扭矩振荡器进行物理储层计算的计算能力的数值分析。传统的自旋电子器件通常由两个铁磁体组成，其中一层（称为自由层）的磁化方向可以移动，而另一层（参考层）的磁化方向是固定的。然而，最近，已经开发出具有两个自由层的器件用于各种实际应用，其中参考层被另一自由层代替。添加另一个自由层通过经由自旋转移效应和偶极磁场的耦合来急剧改变器件的动力学响应。通过对Landau-Lifshitz-吉尔伯特方程的数值模拟，以及对Lyapunov指数和同步指数的统计分析，揭示了具有两个自由层的振子的振幅调制振荡和混沌现象.这样的复杂动态定性地改变物理储层计算的计算能力，因为计算资源是物理系统的动态。短期记忆能力的评估澄清，振荡器与两个自由层具有比传统的振荡器更大的容量。回声状态特性边缘附近的容量增强，即，同时也发现了零同步指数和有限同步指数之间的界限。
A numerical analysis on the computational capability of physical reservoir computing utilizing a spin-torque oscillator with two free layers is reported. Conventional spintronics devices usually consist of two ferromagnets, where the direction of magnetization in one layer, called the free layer, can move while that of the other, the reference layer, is fixed. Recently, however, devices with two free layers, where the reference layer is replaced by another free layer, have been developed for various practical applications. Adding another free layer drastically changes the dynamical response of the device through the couplings via the spin-transfer effect and the dipole magnetic field. A numerical simulation of the Landau-Lifshitz-Gilbert equation and a statistical analyses of the Lyapunov exponent and the synchronization index reveal the appearance of an amplitude-modulated oscillation and chaos in the oscillators with two free layers. Such complex dynamics qualitatively change the computational capability of physical reservoir computing because the computational resource is dynamics of the physical system. An evaluation of the short-term memory capacity clarifies that oscillators with two free layers have a larger capacity than those of conventional oscillators. An enhancement in capacity near the edge of echo state property, i.e., the boundary between zero and finite synchronization index, is also found.